The present invention is directed to the production of organic polysilanes in a safer, simpler and more economic manner than possible by prior art methods. More particularly, the invention is directed to the production of dodecamethylcyclohexasilane and simpler polysilanes.
Organic polysilanes are chemical substances in which there is more than one silicon to silicon bond in the molecule with organic groups also bound to the silicons. The organopolysilanes are of utility as organic intermediates and precursors for high temperature polymers. Dodecamethylcyclohexasilane is of great current interest because it yields reactive silylene when treated with ultraviolet radiation, and because it is a precursor to oriented silicon carbide.
The general method for the production of polysilanes is the treatment of organohalosilanes with an alkali metal, usually sodium, under pressure. The method currently employed for the production of dodecamethylcyclohexasilane involves the reaction of sodium-potasium alloy on dimethyldichlorosilane to yield a complex mixture of polysilanes. The polysilanes are then reequilibrated to the cyclic hexamer. This synthesis is described by R. West in Inorganic Synthesis, page 265 (Wiley 1979).
The synthesis of polysilanes as described above may be represented by the following equation: EQU RR'SiX.sub.2 +2M.fwdarw.(RR'Si).sub.n +2MX
where R and R' are organic groups selected from alkyl, aryl or equivalent groups, usually lower alkyl, X is halogen, and M is an alkali metal or alkali metal alloy.
The above methods have several disadvantages which make the production of polysilanes difficult, dangerous and/or uneconomic. As noted above the treatment of organohalosilanes with alkali metal requires the use of pressure. Also, sodium-potasium alloy is a pyrophoric metal which is extremely danagerous to handle. These and other disadvantages of the prior art are alleviated by the methods of the present invention.